Embodiments of the disclosure relate generally to power conversion systems and methods for converting and providing electrical power to feed an electrical system and, more particularly, to power conversion systems and methods with improved maximum power point tracking capability.
Renewable power, such as solar power generated by solar power generation systems, is becoming a larger source of energy throughout the world. A typical solar power generation system includes one or more photovoltaic arrays (PV arrays) having multiple interconnected solar cells. The solar cells of the PV arrays convert solar energy into DC power. In order to interface the output of the PV arrays to a power grid, a solar power converter is typically used to change the DC power from the PV arrays into AC power to feed a power grid.
Various solar power converter configurations exist for converting the DC power output from PV arrays into AC power. One implementation of a solar power converter has two stages including a DC-DC converter stage and a DC-AC converter stage. The DC-DC converter controls the flow of DC power from the PV arrays onto a DC bus. The DC-AC converter stage converts the DC power supplied to the DC bus into AC power that can be output to the power grid. Existing solar power converters further utilize power converter controller to regulate the DC-DC converter and the DC-AC converter to compensate for various system variables, such as DC bus voltage and AC grid voltage and frequency.
Due to inherent non-linear characteristics solar power sources, it is not easy to accurately predict the optimum operating point of solar power sources. Thus, almost all existing solar power converter controls are configured with a maximum power point tracking (MPPT) function to ensure maximum power is extracted from the solar power source during the solar power generation process. The MPPT function may be achieved by implementing one of a variety of MPPT algorithms such as perturbation and observation (P&O) algorithms and incremental conductance algorithms, for example. When the solar power conversion system is connected to a power grid, implementing such conventional MPPT algorithms have some limitations. One challenge is that a power imbalance may occur at the DC bus from the MPPT output power being larger than the line side output power. Thus, over-voltage problems will be present at the DC bus if the power conversion system is not able to respond quickly to deal with the additional power generated from the power source. The power imbalance challenge may become severe when the power conversion system is connected to a weak power grid which may have large variations of voltage and frequency.
Therefore, it is desirable to provide systems and methods to address the above-mentioned problems.